1. Field of the Invention
This invention relates to a three-dimensional model cross-section instruction system and instruction method. More specifically, it is related to a three-dimensional model cross-section instruction system and instruction method that make it easy to specify the cross-section to be displayed and display the cross-section effectively when viewing the conditions inside a three-dimensional structure.
2. Description of the Related Arts
In recent years, technological progress in workstations has made it possible to process three-dimensional model data rapidly.
When viewing a part located in the interior of a large-scale three-dimensional structure such as one apparatus, a test product is assembled at the actual work site and, if a problem occurs, the apparatus must be disassembled to remove the part causing the trouble. However, if simulated model data are created on a computer, it is then possible to display an interior part causing trouble on the screen while assembling the parts on the screen, and it becomes easy to grasp the location of that part.
For these reasons, when creating a three-dimensional model of an apparatus comprising a number of parts and units it is convenient to be able to display cross-sections. When displaying a cross-section, it is necessary for the user to specify the cross-section to be displayed.
FIG. 1 is a diagram that explains the previous method of specifying a cross-section.
First, for example a three-dimensional model of a three-dimensional object is displayed on the display screen 1101; let us suppose that the user wishes to display a cross-section of this three-dimensional model. In this case, the user first defines a two-dimensional coordinate system on the cutaway surface separate from the coordinate system of the three-dimensional figure (X, Y, Z in the diagram). Then the three-dimensional model is moved toward that cutaway surface. As a result, the shape 1102, which is the part that crosses that cutaway surface, is displayed on the display. That is to say, the figure of the cross-section is displayed by not displaying the part that crosses the cutaway surface of the three-dimensional model (clipping processing). This method is described in, for example, Japanese Patent publication hei3-185578.
Meanwhile, improvement of the method of displaying the cutaway surface has moved ahead of the method of specifying the cutaway surface. For example, display processing such as coloring display, hidden surface display, shadow display, etc. have been quite effective in creating three-dimensional models of individual parts.
In this method, by means of hidden display the figures located in the interior are hidden when the parts are assembled. Therefore, to display the interior the transparency of parts located on the outside is specified and external parts are displayed as translucent. This method is described in, for example, Japan Patent publication hei4-71082.
However, the prior methods each have their own respective problems.
Specifically, the cutaway section in clipping processing is a display method that is used in, for example, defining the virtual limit of display on the display screen; simple rotation of the cutaway surface is possible, but the cutaway surface cannot be given an arbitrary shape, and partial cutting of a section cannot be specified. This creates the problem that, in a three-dimensional model with complicated nesting, such as parts within parts that are in the interior of the apparatus, the inside parts cannot be displayed effectively.
In translucent display processing, the shapes and positions of interior parts can be grasped, but there is the problem that if a correction is to be applied to one part in the interior, since the display is (transparent only translucent) the accurate coloring and shadow pattern of that part are lost. In addition, in translucent display processing, there is the problem that various data conversion calculations must constantly be done for a huge amount of three-dimensional figure data using the transmissivity, making the calculations expensive.
Moreover, whichever method is used, whenever a figure is displayed all figure data must be read in, regardless of whether they will be displayed or not, so that the quantity of data which must be handled is large and considerable time is required for the processing.
When corrections are to be applied to parts in the interior of a model made by assembling a number of parts, and the positions of those parts are to be checked, it is necessary to be able to display cross-sections easily and in a short time, without affecting the condition or position information of parts other than the ones to be corrected.